Lower bearing cone

[shane BBoys]

Hi.
I have 3 bottom steering cones at hand, all varying in size. My frame measures 41.29 daft question is what size should the race be to fit correctly?

Cheers Shane.

[Fast n Furious]

It's not a daft question.
It only needs to be fractionally bigger. 41.4 ish. in your case. ( If you've used verniers for this measurement, then consider the figure as nominal)
If the fit is too tight and takes a lot of force to insert, then they can crack the lower steering columb open. (not good)
Non OEM ones can be larger than 42mm!

I find that I have to machine most of them to size these days so they will knock in comfortably most of the way using a block of wood and a 4lb hammer along with a smear of Loctite bearing lock. I then finish the job off using a long length of M16 stud bar with the contents from my engine mount extractor kit to press it home.

[shane BBoys]

FnF.
Are you saying that the cone should only be 41.4 to fit in my case, and not 42mm? I do have a drift a big hammer a cone in the freezer and a heat gun!
Cheers Shane.

[Fast n Furious]

There's no need for it to be a ridiculously tight interference fit. Like i say...... you risk fracturing the steering tube and it makes them near impossible to remove again. Using too much battering force will damage this outer race cone. Use the threaded bar compression method to pull it in straight.
I've just measured a couple that I have in stock. 1 measured 41.7 which is spanish and the other measured 42.00 from godknowswhereistan. Pattern stuff almost always needs some fettling before it can be reliably used.

[nickw]

This reminds me of the problems I had a couple of years ago. Managed to get old cone out with a lot of effort. I could not get the new one in. Eventually called upon a man who knows (Waddo). It was the cone. He replaced with a cone that fitted. Learnt lesson. Not all cones are equal.

[shane BBoys]

She’s in. Frozen cone heated stem knocked in with the drift and hammer!

Thanks for all your advise.
Cheers Shane.